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RE: Basement wall restrained by wood floor

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I guess we have worse soils to go along with our earthquakes here on the
west coast.   :<0 

 However, for the small cost of a little rebar and the TREMENDOUS problems
it prevents, I wouldn't even think of using plain concrete for the walls.
(Admittedly, most of my practice has been in Zone 4, near fault areas where
the code disallows unreinforced concrete except for Footings in Group R,
Division 3 or Group U, Division 1 Occupancies and for ground-supported
nonstructural slabs. But, many of the unreinforced basement walls of
buildings I have observed that were built before the current code provisions
began requiring reinforcement have performed miserably due to temperature,
shrinkage and earth pressure loadings)
 
Regards,
Bill Cain, SE
Oakland, CA


	-----Original Message-----
	From:	Jie Lu, P.E., S.E. [SMTP:jayjielu(--nospam--at)worldinter.net]
	Sent:	Thursday, August 26, 1999 6:54 AM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Re: Basement wall restrained by wood floor

	James:

	I agree with you. Furthermore, in Midwest the basement wall usually
is plain
	concrete. Per BOCA '99, Page 215, 8" plain concrete wall can span 8
ft with
	7 ft
	unbalanced fill of GW, GP soils (30 pcf). The only rebars are
usually
	(2)-#4 horizontal at the top and bottom of the wall. Stress analysis
would
	indicate
	that the concrete stresses comply with ACI 318-95, Plain Concrete
Chapter.
	The cost difference between reinforced retaining wall and the plain
concrete
	wall is obvious.

	Jie Lu, P.E., S.E.
	J. Lu International, LLC



	. ----- Original Message -----
	From: James F Fulton <James_F_Fulton(--nospam--at)RohmHaas.Com>
	To: <seaint(--nospam--at)seaint.org>
	Sent: Thursday, August 26, 1999 7:14 AM
	Subject: Basement wall restrained by wood floor


	> In 99.9% of the residential construction I've seen, the basement
wall is
	> supported by a strip footing, usually 20" wide or so. This type of
wall
	> relies on the support at the top provided by the first floor. In
one
	> direction, the direction of the floor joists, not only the floor
deck but
	> also the joists act to provide the restraint. Pretty stiff and
pretty
	strong
	> in this direction. In the other direction, parallel to the joists,
a
	blocking
	> or bridging system has to be used to transfer the transverse shear
at the
	> bottom of the rim joists, that bears on the sill plate that's
anchored
	bolted
	> into the top of the wall, to the level of the floor deck.  In this
case,
	the
	> floor deck is indeed providing most of the strength and stiffness
it would
	> seem. But I don't see why it cannot be relied upon do its job. To
design
	the
	> wall as a cantilever against backfill loads has expensive
implications for
	> residential construction now that a structural footing is needed.
	>